Amount of Infants' Food Intake Affected by Breastfeeding, Study Finds

< May. 12, 2010 > -- A new study indicates that babies who are fed directly from the breast in early infancy tend to consume less later in infancy than babies who are bottle-fed.

These findings regarding self-regulation of food intake may help explain why past research has found that breastfeeding protects against obesity.

The study results were released this week in advance of publication in the June print issue of the journal Pediatrics.

Direct Breastfeeding is Key

"Infant self-regulation can indeed be affected by how the milk is delivered to the baby," says the study's lead author, Dr. Ruowei Li, a medical epidemiologist at the Centers for Disease Control and Prevention (CDC). "The more infants were fed with a bottle, the more likely that they would empty a bottle in late infancy," adds Dr. Li.

"Infancy is a crucial period that has an impact on self-regulation, and many other studies have shown that infant growth and rapid weight gain have an effect on obesity later," Dr. Li says. "Obesity prevention needs to start in infancy."

Dr. Li explains that this means parents who feed their baby either expressed breast milk or formula with a bottle need to pay special attention to their baby's feeding cues.

Full-Term Infants Followed for 12 Months

The study looked at 1,250 full-term infants who weighed more than 5 pounds at birth. Their mothers completed a monthly feeding questionnaire until the babies were 12 months old.

With 1-month-old babies, 52 percent of the mothers were breastfeeding exclusively, and 41 percent were formula-feeding. The remaining babies were fed expressed milk or some other type of milk, according to the study. When the babies were 6 months old, just 27 percent of the mothers were breastfeeding exclusively, and 66 percent were formula-feeding.

When the babies were between 6 and 12 months old, the researchers asked the mothers how often the babies emptied their cup or bottle.

The study authors found that among infants who were breastfed exclusively in early infancy, 27 percent emptied their cup or bottle in late infancy, compared with 68 percent who were bottle-fed exclusively and 54 percent who were given both breast and bottle in early infancy.

Feeding Cues Differ between Breastfeeding and Bottle Feeding?

Dr. Li believes there may be several reasons for the difference in feeding amounts in the older infants. For starters, she said, breastfeeding is generally directed by the baby, but bottle-feeding is directed by the caregiver and could lead to overfeeding.

"Mothers or other caregivers may push the baby to empty the bottle, but if they're breastfeeding, there's no way to visualize how much the infant is consuming," says Dr. Li.

Another possibility is that a mother's milk changes from one feeding to the next, and even during a feeding, Dr. Li says. Depending on what the mother has eaten, the milk may taste differently. And, she says, the fat content is much higher near the end of a feeding, and that might send a signal to the baby that it is almost time to stop.

Another factor might be that an infant who is breastfeeding is not getting milk the entire time, explains Dr. Li. The baby suckles for a few minutes before the mother starts releasing milk, but with a bottle, that non-nutritive suckling time does not happen.

Breastfeeding's Benefits Reinforced

Dr. Deborah Campbell, director of the neonatology division at the Children's Hospital at Montefiore in New York City, describes the research as "another study that stresses the importance of breastfeeding."

And, "if you can't breastfeed, this study shows the importance of learning to recognize your infant's cues and to respect those cues," Dr. Campbell says. "When we're bottle-feeding, we often override babies' ability to self-regulate their intake."

But when babies stop sucking, turn their head, or thrust their tongue out, she says, then the baby has had enough to eat.

"Parents are often concerned that if a baby doesn't get a full feeding that the baby will wake up hungry soon after," Dr. Campbell explains. "And, that may happen. But you have to respect the cues your baby is giving you."

Dr. Li agrees. "Feeding directly from the breast should be your first choice, if possible," she said. "If it's not, be aware that you don't overfeed. Pay attention to the signs your baby gives you. Babies are born with the ability to self-regulate their milk intake."

Always consult your child's physician for more information.

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Benefits of Breastfeeding

There are many reasons why breast milk is the best milk.

Nutrients: Human survival depends more on brain power than on strong muscles, rapid growth (rapid maturity), or body size, so your milk is rich in the nutrients that best promote brain growth and nervous system development. Research has found that breastfed babies perform better on different kinds of intelligence tests as they grow older. They also develop better eye function. This is due mostly to certain types of fat (fatty acid chains) in human milk, which are not available in artificial formulas.

The sugar (carbohydrate) and protein in breast milk are also designed to be used easily and more completely by the human baby. Your milk is the perfect first food to help your baby achieve every aspect of ideal growth and development.

The American Academy of Pediatrics recommends that all breastfed and partially breastfed babies receive a supplement of 400 IU per day of vitamin D beginning in the first few days of life. Your baby's physician can recommend the proper type of vitamin D supplement for your baby.

Anti-infective properties: Only human milk is alive with many different kinds of disease-fighting factors that help prevent mild to severe infections. Babies who are fully or almost-fully breastfed, or breast milk-fed babies, have significantly fewer gastrointestinal, respiratory, ear, and urinary infections. Antibodies in human milk directly protect against infection.

Other anti-infective factors create an environment that is friendly to "good" bacteria, referred to as "normal flora," and unfriendly to "bad" bacteria, viruses, or parasites. Human milk also appears to have properties that help a baby's own immune system work best. If your baby does become ill when breastfeeding and receiving your milk, the infection is likely to be less severe.

Easily digested: Since nature designed human milk for human babies, your milk is the most easily digested food your baby can receive. A nutritious, yet easily digested first food is important for a baby's immature digestive tract. Your baby uses less energy, yet breaks your milk down more completely into its basic ingredients, so the nutrients, anti-infective factors, and all the other ingredients in your milk are more available to fuel your baby's body functions and to promote your baby's growth and development.

Bio-availability: Bio-availability is a fancy way of referring to how well the body can use the nutrients in a food. The high bio-availability of nutrients in human milk means your baby gets more benefits from the nutrients it contains - even for nutrients that appear in lower levels in breast milk when compared to artificial formulas (because your baby's body can absorb and use them most effectively). It also means your baby saves the energy that would be needed to eliminate any nutrients he/she had difficulty digesting or using.

Suitability: Your milk is best suited to, and so it is more gentle on, your baby's body systems. The suitability of your milk plays a role in your milk's digestibility, and it allows your baby's body to function most efficiently while spending a lot less energy on body functions. Suitability is also thought to be one reason that breastfed babies are less likely to develop allergic-related skin conditions and asthma.

The digestibility, bio-availability, and suitability of your milk means that your baby's body is able to work less yet receive more nourishment.